Present clutch technology uses acceleration and centrifugal action to engage the clutch, but once engaged the clutch cannot be disengaged while being rotated at a rotational speed (revolutions per minute) above the operating limits of the power source. This is due to centrifugal forces in the clutch. Other clutch devices use electro-mechanical solenoids which are difficult to disengage while a gear portion is under load. In automotive clutch applications, such as sliding doors, it is desirable to provide a power drive system for driving the sliding door in movement between an open position and a closed position, where the power drive system accommodates shifting between manual and positively driven powered operation of the door at any position along the path of movement.